please help 84. :i 74% 3:33 PM MAT 143-300 Fal 2017 Lakisha Ravix & 12/7/17 3:33

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please help

84. :i 74% 3:33 PM MAT 143-300 Fal 2017 Lakisha Ravix & 12/7/17 3:33 PM Homework: HW sec 4.8 Exponential Growth & Decay Score: 0.5 of 1 pt 4.8.3 Save 2of7C2 complete) Score: 12.86%, 0.9 of 7 pts Question Help D 00441 Strontium 90 is s radiosctive material that decays according to the function Alt)-A wh at time t (in years). Assume that a scientist has a sample of 500 grams of strontium 90 (a) What is the decay rate of strontium 907 b) How much strontum 90 is left after 30 years? (e) When will only 200 grama of strontium 90 be left? where Ag is the initial amount present and A is the amount present (a) What is the decay rate of strontium 907 % (Type an integer or a decimal. Include the negative sign for the decay rate) ur answer in the answer bax and then click Check Answer Clear A

Explanation / Answer

a)   k=decay rate = -0.0244 year^-1

b) if t=30 years

A(t) =500g*e^-(0.0244*30)=240.47g (Strontium left after 30 years)

c) 200g =500g*e^-0.0244t

Solve for t

-> t= 37.55 years

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